Studies of network organization and dynamics of e-beam crosslinked PVPs: From macro to nano

In this work the influence of poly(N-vinyl pyrrolidone) (PVP) concentration in water on the organization and dynamics of the corresponding macro-/nanogel networks has been systematically investigated. Irradiation has been performed at the same irradiation dose (within the sterilization dose range) and dose rate. In the selected irradiation conditions, the transition between macroscopic gelation and micro-/nanogels formation is observed just below the critical overlap concentration (~1 wt%), whereas the net prevalence of intra-molecular over inter-molecular crosslinking occurs at a lower polymer concentration (below 0.25 wt%). Dynamic-mechanical spectroscopy has been applied as a classical methodology to estimate the network mesh size for macrogels in their swollen state, while 13C NMR spin-lattice relaxation spectroscopy has been applied on both the macrogel and nanogel freeze dried residues to withdraw interesting information of the network spatial organization in the passage of scale from macro to nano.